JPS5845181B2 - How to connect external leads of semiconductor devices - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for connecting external leads of a semiconductor device.

Conventionally, there are two main methods for leading external leads in semiconductor devices, one of which is Al.

One is the wire bonding method using thin metal wires such as Au, and the other is the multi-bonding method using an external lead frame.
This is a bonding method.

The former is a bonding method that is currently widely used, and is further divided into thermocompression bonding and ultrasonic bonding, which are well known to those skilled in the art.

The hot glue bonding method is a bonding method that is used when A and U wires are used.The tip of the Au wire is exposed to a flame to form a ball, and pressure is applied from above to bond it to the bonding pad of the semiconductor element. It is something to do.

This method has relatively strong bonding strength with no directionality.

The ultrasonic bonding method is a bonding method used when using Al wire, and the tip of the wire is pressed against the bonding pad part and bonded using ultrasonic vibration. Although heating is not required, there is a problem with the reproducibility of ultrasonic output.

In contrast to the wire bonding method described above, the multi-bonding method mainly uses an ultrasonic bonding method or an electric resistance heating bonding method.

Here, a subafida bonding method known to those skilled in the art as a multi-punching method will be described.

The spider web-shaped aluminum foil, that is, the external lead frame, is press-formed to match the placement of the bonding pads of the semiconductor device, and is made up of 10,000 to 25,000 continuous threads, which are wound onto a reel. ,
The aluminum foil has a thickness of 50 to 70 μm, and semiconductor elements are sequentially bonded to this continuous strip supplied from a reel, and then wound onto the reel again.

゛An ultrasonic bonding method is used to bond the F conductor element and aluminum foil.It goes without saying that the lead frame may be supported by a resin material, but there are other methods other than using aluminum foil as the lead frame material.
A method using plated Cu foil is also known, and in this bonding method, a T tool heated by electrical resistance is pressed from above the lead and bonded to an Au bump on a bonding pad portion provided with an Au mating.

This bonding utilizes the alloying reaction that occurs at the relatively low melting point of Au-8n.

If aluminum is used as the wiring metal or bonding pad material of the semiconductor element, it is best to use aluminum as the material for the lead frame.
Other metals are undesirable due to many metallurgical problems.

This is known from the fact that harmful intermetallic compounds such as Au-Al are formed, and dielectric breakdown due to Sn whiskers, which often occurs when Sn is used, is known.

Currently, when aluminum foil is used as a lead frame material, an ultrasonic bonding method is used.

However, as described above, in the ultrasonic bonding method, the bonding strength tends to be uneven, and this drawback is particularly emphasized when simultaneous multi-point bonding is performed in the multi-bonding format.

In addition, as mentioned above, the thickness of the lead tip is 50 to 70 μm, but the width of the lead tip determined by the dimensions of the bonding pad is about 100 μm or more, and its mechanical strength is I can't say it's enough.

It goes without saying that when handling lead frames, it is better to have a little more mechanical strength.

Further, after bonding, the leads must be machined and bent in order to prevent the bonded leads from coming into contact with the semiconductor element substrate, so-called pellet contact, and causing an electrical short circuit.

In order to solve the above-mentioned drawbacks, an object of the present invention is to provide a lead with a small mechanical strength to a certain degree of strength by having a fine buckoon, and to improve the reliability of a semiconductor device. The object of the present invention is to provide a connection force method for external leads of a conductor device (1") that does not cause pellet contact without bending the conductor device.

A feature of the present invention is that in the bonding step in the manufacturing process of multi-bonding type semiconductor devices, this bonding bottom plug connects the end portion of the external lead to the semiconductor substrate in which at least the tip end portion of the external lead including the bonding portion is entirely covered with a resin material. and placing all or a portion of the external lead end on the upper bonding pad (including the bump) and having a high energy density such as a laser beam or an electron beam. and a step of melting using an energy source.

A method for connecting an external lead of a semiconductor device includes electrically connecting the external lead and the bonding pad.

Next, embodiments of the present invention will be described with reference to the drawings.

The present invention uses lead frame materials widely used by those skilled in the art, such as Al, Cu, copal (FeN-Co alloy), thermosetting resins such as polyimide resin, epoxy resin, and silicone resin, and thermoplastic resins such as Teflon resin. This can also be easily carried out using a resin-coated lead frame, and an example will be described below in which a lead frame such as the spider bonding method known to those skilled in the art is used as a multi-bonding method.

FIG. 1 shows an overview of the bonding method, in particular the relative positions of the semiconductor component 1, the external leads 4 and the beam 5 with high energy density, such as a laser beam.

Further, regarding the bonding pad portion shown in FIG. 1, FIG. 2 shows an enlarged cross-section of the vicinity of one bonding pad portion.

That is, the end portion of the outer wire 4 covered with the resin layer 3 is placed so as to be included on the bonding pad 2a on the semiconductor element 1.

A suitable jig is required for this operation, but this will be omitted.

As for the constituent materials, Al is used for the wiring layer 2 on the semiconductor device 7'-1, Cu is used for the external lead material, and Teflon resin is used for the resin (resin layer 3) covering the external leads 4.

When a laser beam 5 is irradiated onto the external lead as shown in FIGS. 1 and 2, the resin in the portion of the external lead irradiated with the laser beam evaporates or thermally decomposes.

This phenomenon occurs between the external lead 4 and the bonding pad portion 2.
The same can be said about the resin between a and a.

That is, the resin evaporates and the molten external lead material flows out into the decomposed portion, forming an electrical conduction path 6 between the external lead 4 and the bonding pad 2a, and the external lead 4 and the bonding pad 2a are connected as shown in FIG. electrically connected as shown.

Figure 3 shows the bonding process of a semiconductor element after bonding is performed by irradiating a laser beam 5 from above the external lead.
This shows the area around the pad.

In the above bonding process, the following three factors must be met in order to ensure electrical continuity between the external lead and the bonding pad portion.

(1) Output of energy source such as laser beam (2) Material and thickness of external lead material (3) Material and thickness of resin layer on the surface of external lead material (
1) can be explained as follows using a laser beam as an example.

The power of the laser beam must be sufficient to melt the outer lead metal material, but at the same time it must be less than the power required to vaporize the outer lead metal material.

Since the melted portion has a small area and is a thin plate, it can be said that continuous wave laser light is more advantageous because it can take a longer irradiation time than output light that has pealing, such as a pulsed laser.

Regarding (2), it is even more difficult to say because the depth of penetration with a constant laser output varies depending on the material and plate thickness of the external lead material.

In this regard, the seeding of the
of the IEEE ) vol.
5 7.

NO2, Fe1ruary, 1969, Pl 14
There is an explanation in ~l 47.

In actual work, the external lead material used is (
iq, it is necessary that the plate thickness be sufficiently large relative to the resin layer.

The thickness of the external lead material currently used in the multi-bonding method is less than 100 .mu.m, and it can be said that it is sufficient if the resin layer to be coated is about the same thickness, 10 .mu.m or less.

It is also effective to raise the bonding pad portion as shown in FIG. 4 in order to improve bonding workability and bonding mechanical strength.

This raised area 7 is called a bamboo, and because of the bonding pad portion made of a thin metal layer, the effect of heating by laser light or electron beam on the active area of the semiconductor element is reduced.

To briefly explain FIG. 4, in this case, the ends of the external leads 4 covered with the resin layer 3 are installed on the bamboo L in the same manner as described above, and the other methods are the same as described above. Of course, the external lead 4 and the bonding pad portion can be electrically connected by using the external lead 4 and the bonding pad portion.

The present invention is not limited to the present embodiment, and various applications and modifications are possible without restricting the scope of the patent claims.

By using the method for connecting external leads for a semiconductor device according to the present invention described below, the following effects can be obtained.

(1) With a fine pattern, nodes with no mechanical strength can be given the strength of dust to a certain extent.

(2) In general, considering the trend of semiconductor devices gradually becoming subsystems such as I-transistors and integrated circuits, the semiconductor elements themselves are protected by hard materials such as silicon nitride, which is called packageless packaging. This has the potential to eliminate the need for placing the container in a conventional container made of ceramic or metal material.

However, if there is no protection for the external leads, it is not possible to improve the reliability of the semiconductor device, but since most of the defects in semiconductor devices occur in the lead parts including the bonding parts, Thus, reliability can be improved by covering at least the tip of the external lead, including the bonding part, entirely with a resin material to protect the lead.

In particular, when the entire surface of the lead is covered with resin to protect the lead as in the present invention, reliability is further improved.

In this case, it is particularly effective when aluminum is used as the material for the lead frame.

That is, aluminum has poor moisture resistance and is easily corroded, but this can be prevented by coating it with resin.

(3) After bonding, it is possible to prevent electrical short circuits due to pellet touch even if the external leads are folded.

[Brief explanation of drawings]

1 to 3 show an embodiment of the method for connecting external leads for a semiconductor device according to the present invention, FIG. 1 is a diagram showing an outline of the bonding method, and FIG. 2 shows the bonding pad portion of FIG. 1. FIG. 3 is a cross-sectional view of the bonding pad portion after bonding is performed at the bonding pad portion shown in FIG. 2, and FIG. 4 is a method for connecting external leads for a semiconductor device according to the present invention. FIG. 4 is a cross-sectional view of a bonding pad portion after bonding obtained by applying the present invention to a semiconductor element with bumps, showing another embodiment of the present invention.

Claims (1)

[Claims] 1. In the bonding process in the manufacture of semiconductor devices using the multi-bonding method, the bonding process involves bonding the ends of external leads whose entire surfaces, including at least the bonding portion, are covered with a resin material, onto bonding pads on a semiconductor substrate. and then melting at least a portion of the end of the external lead, the step of melting at least a portion of the end of the external lead and the bonding
A method for connecting an external lead of a semiconductor device, the method comprising electrically connecting the external lead to a pad.